P0593Generic code

P0593 Code: Cruise Control Multi-Function Input B Circuit High

The P0593 code means the computer sees a fault in the signal from the cruise control switches, a high signal on multi-function input B. Cruise control is disabled, and the rest of the vehicle works normally. A worn steering wheel clockspring is the usual cause.

Severity
Low
Can I keep driving?
Yes, no immediate risk
Estimated cost
$20 to $400
Difficulty
Medium
System
Idle and Speed Control
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0593 code means

The cruise control switches, on the steering wheel or on a stalk, send their commands to the computer over one or more wires. Many manufacturers use a single line with a different resistance for each button, and the computer recognizes the pressed button by the voltage it measures.

The P0593 code means the computer sees a signal that does not correspond to any button, a signal that stays fixed as if a button were always pressed, or a signal that does not match the second control line. For safety, it disables cruise control.

The most frequent cause is the clockspring in the steering wheel, which connects the buttons to the vehicle through a ribbon that wears out as the wheel turns. Another common cause is buttons that are dirty or have had liquid spilled on them.

Always start with the simplest checks: fuse, relay and connector. Then check power, ground and signal with the component connected (using back-probe pins), and finally the continuity of each wire to the computer. Replace the component only if all of that is good.

P0593 code symptoms

  • Cruise control that does not work.
  • Check engine light or cruise control light on.
  • Sometimes the horn or the steering wheel buttons do not work either (clockspring).

Likely causes of the P0593 code

  1. Damaged steering wheel clockspring. The internal ribbon breaks with use.
  2. Steering wheel buttons that are dirty or damaged by spilled liquids.
  3. Control module connector with an intermittent contact.
  4. Brake switch, if it affects the cancel signal.

How to diagnose the P0593 code step by step

  1. Watch the status of each button on the scan tool as you press it. Only the pressed button should change.
  2. Measure the switch resistance in each position and compare it with the manufacturer table.
  3. Check the clockspring if the horn, the airbag light or the steering wheel buttons also fail.
  4. Check the brake switch.

How to fix the P0593 code

  • Replace the clockspring or the steering wheel controls.
  • Clean the button contacts.
  • Repair the wiring.
  • Clear the code and test cruise control.

Technical reference data

  • Resistor ladder controls: each button gives a different voltage on the same line.
  • Reference values only: check the manufacturer data for your vehicle.

Brand-specific notes

When you work on the steering wheel, disconnect the battery and wait a few minutes first. The driver airbag can deploy.

P0593 on Ford

On many Ford vehicles the clockspring is a frequent failure.

P0593 on GM

On many GM vehicles the clockspring is a frequent failure.

P0593 on Chrysler

On many Chrysler vehicles the clockspring is a frequent failure.

Frequently asked questions about P0593

Can I drive with the P0593 code?
Yes. It only affects cruise control. The engine, brakes and the rest of the vehicle work normally, and there is no safety risk while driving.
What is the clockspring?
It is a coiled ribbon in the steering column that connects the airbag and the buttons to the vehicle even as the steering wheel turns. When it wears out, the buttons stop working.
Is it dangerous to remove the steering wheel?
Yes, because of the airbag. Follow the manufacturer procedure, disconnect the battery and wait before you touch anything.
How much does it cost to fix P0593?
Between $20 and $400. Cleaning a contact or repairing a wire is cheap, and a clockspring or steering wheel controls cost more.
What does the P0593 code mean?
The P0593 code is a generic OBD2 code for a high signal on cruise control multi-function input B. The computer does not accept the switch signal, so it turns the system off.
What is the most common cause of P0593?
A worn clockspring in the steering wheel, followed by dirty buttons and a loose connector.

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